Introduction: Sacrum consists of five fused sacral vertebrae. These are fused to provide strength and stability to the pelvis and transmit the weight of the body to the pelvic girdle through the sacro-iliac joints. The vertebral column can bear a weight of nearly 355 kg without crushing and a tearing strain of nearly 152 kg. Its weakest part is in the neck, which normally carries least weight. Lumbosacral transitional vertebrae (LSTV) are congenital anomalies of the lumbosacral region, which includes sacralisation of fifth lumbar vertebra and lumbarisation of first sacral vertebra observed for the first time by Bertolotti in 1917. This condition occurs due to defect in the segmentation of the lumbosacral spine during development and the combined effect of mutation of homeobox (HOX 11) & paired-box (PAX1 & PAX9) gene expression causes several types of sacralisation. Low back pain is quite a common ailment affecting about 80% of the population in their life time. This abnormality can be diagnosed by plain radiography.

Materials and Methods: In the present study 100 adult human sacra were examined in the department of Anatomy, Mysore Medical College and Research Institute, Mysore, Karnataka.

Conclusion: Knowledge of sacralisation is not only enlightening for the orthopaedic surgeons, also vital for the Clinical Anatomists, Radiologists, Forensic experts, Morphologists, Architectures and Anthropologists. Hence we are presenting such variation with emphasize on its clinical relevance. Incorrect numbering during the planning of spinal surgery may have serious consequences.